It is generally desirable in semiconductor integrated circuit devices to provide barrier layer films for use in conjunction with conductive materials, such as those used as interconnect devices or wiring layers. Conductive materials are generally isolated from other features of semiconductor integrated circuit devices by means of a dielectric material. In damascene processing, the interconnect structure or wiring pattern is formed within grooves or other openings formed within a dielectric film. In non-damascene processing techniques, the conductive, interconnect structures are formed over a dielectric film.
Barrier layer films are needed between the dielectric material and the conductive material in order to prevent portions of the conductive material from migrating through the dielectric material and into other active device features. Such migration can cause inter-level or intra-level shorts through the dielectric material. When portions of the conductive material migrate into underlying silicon such as a silicon substrate commonly used in the semiconductor industry, various device performance characteristics can be adversely affected. For example, junction leakage may result, and threshold voltage (V.sub.t) levels of the transistors formed within the silicon substrate, may be shifted. In many cases, device functionality can be destroyed.
The above effects are of a particular concern when copper (Cu) is used as the conductive interconnect material since copper is most mobile throughout semiconductor structures. Copper is favored in the semiconductor integrated circuit manufacturing industry because of its superior conductivity. As such, when copper is used as the conductive material within damascene structures, the conductive copper material must be virtually encapsulated within a barrier layer film. Barrier layer films have come into use to separate conductive films such as copper from the dielectric films over which, or in which, they are formed. Barrier layer materials also find utility in contact regions wherein a conductive film is contacted to another conductive film, or to a region of a semiconductor device. In this application, the barrier layer material suppresses spiking between the conductive materials, or between the conductive material and the semiconductor material.
The art of semiconductor manufacturing provides a number of conventional barrier materials. Each of the conventional barrier materials includes a limitation, however, which limits its effectiveness when used in conjunction with copper films which are most desirable in the art, but which are also most mobile throughout semiconductor structures. An example of a barrier material conventionally used in conjunction with copper, is tantalum (Ta). A drawback associated with the use of tantalum in this application, is the inability of tantalum to adhere satisfactorily with conventionally used dielectric films such as silicon dioxide (alternatively referred to as "oxide"). Because of the limitations associated with the use of tantalum, tantalum nitride (TaN) has also been used as a barrier material in conjunction with copper. Tantalum nitride (TaN) offers the advantage that it adheres well to oxides and other dielectric films. A drawback associated with the use of tantalum nitride as a barrier layer material, however, lies in the poor atomic matching between tantalum nitride and copper along the interface formed between the materials. As such, a Cu--TaN film structure is more highly strained then a Cu--Ta film structure. Atomic matching between copper and tantalum nitride is deficient on certain atomic planes.
Other materials proposed and sometimes used as barrier layer materials in conjunction with copper, also exhibit shortcomings which make them unsuitable for use in conjunction with copper films. For example, titanium nitride (TiN) also exhibits poor atomic matching on certain atomic planes along the interface it forms with copper. Pure titanium (Ti) is generally considered unsuitable for use as a barrier layer material in conjunction with copper, because titanium combines with copper to form an inter-metallic compound which lowers the conductivity of the copper film. Titanium is a material which adheres well to dielectric materials such as oxides.
What is needed in the art is a barrier layer material suitable for use in conjunction with copper and other conductive materials, which adheres well to oxide and other dielectric films, and which produces a low strain or a hetero-epitaxial relationship with the conductive film with which it forms an interface. An object of the present invention is to provide such a barrier layer film, and a method for forming the same.